Lieut. Humphrey Fairweather, R.N., in his latest disastrous attempt to prove to the Navy that his rocket invention is better than theirs only succeeds in convincing them that no guided-missile station will be safe until he is out of harm's way. The Navy's problem is solved---they think---when it is discovered that "H.M.S. Berkeley", an ancient destroyer now ending her days as the oldest member of the "Mothball Fleet" has been inadvertently left without a commanding officer for nearly two years. Fairweather's appointment is greeted with extreme alarm by the ship's skeleton crew who, under the inspired leadership of their slick, quick-witted and enterprising Irish bosun, have been happily building up a highly profitable business association with the local village. Their base of lucrative racketeering is being threatened with the arrival of Fairweather. But, it is fortunate for the crew, however, that in addition to his very hazy knowledge of a Captain's duties, Fairweather is immediately engrossed in the dual task of building yet another rocket and also getting to know the curvaceous, sexy French niece, Susanne, of the local publican---one of the ship's best customers.